Iron oxidation state in Cr-spinels by electron microprobe X-ray emission spectroscopy of Lα,β lines.

[Marco E. Ciriotti]

Referenza:
▪ Votyakov, S.L., Zamyatin, D.A., Danilenko, I.A., Chashchukhin, I.S. (2023): Determination of the Iron Oxidation State in Cr-Spinels by Electron Microprobe X-ray Emission Spectroscopy of Lα,β lines. Zapiski RMO, 152(3), 98-112.

Abstract:
The degree of oxidation of Fe, Cu, Eu, Ce, etc. ions in minerals is an important indicator of the redox conditions of their formation and evolution. In this work, the features of X-ray emission Fe L α,β spectra (XES) obtained using a Cameca SX100 microprobe and Mössbauer spectra of Cr-spinel of various compositions from ultramafic rocks of the Urals are studied. From a large collection of samples using microprobe data on grain composition and homogeneity, as well as the Fe3+ / in-lab comparison samples (RC) of chrome spinel were selected, having typical Mössbauer spectra, which can be approximated by doublet components from Fe ions Fe2+ and Fe3+. It is shown that, up to the error of determination, the values ​​of Fe3+ / falling in the range of 8–31%, coincide with those obtained within the framework of a calculation approach based on microprobe data on the composition grains and the assumption that the mineral is stoichiometric Fe2+.